Chinese Gold Farmer
Not to be confused with a regular Farmer, Gold Farmers are players who stay online extremely long hours and farm mobs for the purpose of selling the in-game money they accumulate for real-world money. Gold Farmers then take this money and attempt to sell it to other people through several web sites and auctions in exchange for real-world money. (From www.wowwiki.com/Gold_Farmer)

And now there is a documentary coming out about the bad working conditions of these players.